1. Field
Embodiments of the invention relate to the field of integrated circuit packaging and, more specifically, to microprocessor flip chip packaging.
2. Background
One method of connecting a semiconductor die onto a package substrate is known in the art as controlled collapse chip connection (C4) flip chip manufacturing. Flip chip manufacturing includes a semiconductor die having contact pads (e.g., electric terminals) placed on one side of the die so that it can be flipped over and bonded with adhesive with the contact pads providing an electrical connection with contact bumps on a package substrate. Such adhesives are typically filled fine silica particles in order to compensate for differences in coefficient of thermal expansion (CTE) between flip chip components. It is therefore desirable that adhesive formulations have high filler concentrations so as to more closely match the CTE of the components comprising the flip chip device.
A common method of applying such adhesives is to dispense a small amount of liquid adhesive along the edge of the die allowing it to flow under the die via capillary action. While this process has proven to be useful it has several limitations related to cost and adhesive formulation. Cost is relatively high because the assemblies must be individually handled numerous times in order to dispense the adhesive. The amount of filler that can be formulated into such as adhesives is quite limited because the material must have a relatively low viscosity in order to effectively flow under the die via capillary action. Typical capillary underfilling adhesive materials are limited to filler concentrations no greater than 70% by weight, thus limiting the ability to tailor the CTE of the material to values more closely matching those possessed by the other components comprising the flip chip device.
In addition, problems occur when the adhesive used to bond the die with package substrate sets between the contact pads and contact bumps. For example, when the adhesive is set between the contact pads and the contact bumps, the electrical connection between the die and the package substrate is lessened. That is, the adhesive interferes with the electrical connection between the die and the package substrate.